I have noticed this in my own tanks. A few things I have done is tested straight tap water and then tested the conditioner water right after conditioning it. I have noticed that my conditioner changes the pH.

Many other things can change pH as well. Certain decor can do it. Some rocks and clay pots have been proven to increase the pH, as well as salt. I know that IAL decreases the pH. My tap water has always been 7.4 but my tanks are at 8. Sometimes the pH in my tanks differ because I use epsoms for my boys sometimes. They both get constipation issues sometimes.

If they aren't acting strange, I wouldn't worry too much. I have been having this issue with the tap and tank pH being extremely different since I set them all up, but my fish are acting fine, so I don't over-worry.

Anything that causes the pH to change quickly would be stressful. If you were to suddenly add/remove salt, use pH up or down, or switch them suddenly from one water source or another, it would cause issues.

If you don't do that and acclimate them properly for each water change and do changes consistently (the same each time) I don't think its an issue.

I really wonder if the presence of dechlorinator in the water skews the test results.

Ayala it sounds like you have really low KH. The conditioner should honestly not change the pH by a significant amount. Low KH is not good for fish at all because it means that your pH just does whatever the heck it wants to do, causing stress on your fish.

I'm watching this thread closely. One of the LPS employees pulled me aside and gave me a heads up that the city's tap water is pretty high in it's PH. I tested today and low and behold, it's ~8.4 before I put the water conditioner in. After that it becomes ~ 7.4.

Ayala it sounds like you have really low KH. The conditioner should honestly not change the pH by a significant amount. Low KH is not good for fish at all because it means that your pH just does whatever the heck it wants to do, causing stress on your fish.

Thanks - I'm not exactly sure what kH is and I don't have a test kit for it. I've been looking at the website for our city's water supply and parameters. However, there are 12 different ground wells our water comes from and I don't know which area I am in.

Saw some pretty scary things that can be present in our water because of the farmers, drainage, and the fact that it is ground water.

My tanks pH don't really fluctuate. They stay the same unless I add salt to a tank. It's just the pH is vastly different in the tanks from the straight tap water.

I've had one of my fish for over a year, now, using dechlorinated tap water.

I know you had a spike in the pH - unsure if possibly the test came out wrong, etc.. but since your pH is 7.5, I will warn you about using pH Down. Unsure what number it was "off the charts"..

pH down will lower it for a very short time... then it will raise right back up. Lowering it down and having it raise back up will HARM and could easily KILL the fish. NO need to use pH up/down at all - these aren't discus which need very specific numbers.. these are bettas that are very tolerant of a very wide range of pH and are fine when it goes up/down naturally because it's nice and gradual.

But putting in liquid to change it will do NO good, just risk the health of your fish. All you are going to do is cause what is commonly referred to as a "pH crash" which has been known to kill off entire aquariums in a matter of hours.. pH Down is very unstable. Trying to get it lower will cause it to crash - low pH have no buffering capability.. so if you get it too low and then do a water change and the new pH from the water is a bit higher it will crash it as well.